Distance measurement method and system, and processing software thereof

ABSTRACT

A distance measurement system and method are provided. The distance measurement method first projects a light beam with a speckle pattern to reference planes and an object to allow the reference planes and a surface of the object each have an image of the speckle pattern, the speckle pattern having a plurality of speckles. Next, images of the speckle pattern reflected by the reference planes are captured to generate reference image information, and an image of the speckle pattern reflected by the surface of the object is captured to generate an object image information. A processing module which may be a processing software can compare the object image information with the reference image information to obtain several similarity scores. If the most the most similarity score is greater than a threshold value, the processing module identifies the corresponding reference plane, thereby computing the position of the object.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 099129974, filed on Sep. 3, 2010. The entirety of theabove-mentioned patent application is incorporated herein by referenceand made a part of this specification.

FIELD OF THE INVENTION

The present invention relates to distance measurement, and moreparticularly to a three dimensional (3D) distance measurement method andsystem.

BACKGROUND OF THE INVENTION

Currently, distance measurements include contact distance measurementsand non-contact distance measurements. Wherein the contact distancemeasurements are conventional, and an example of which is calledcoordinate measuring machine (CMM). Although the contact distancemeasurements have been very precise, as the contact distance measurementshould contact the object, probes of the contact distance measurementinstruments may damage the object. Therefore, the contact distancemeasurement instruments are not suitable for expensive objects.

Relative to the conventional distance measurement instruments, thenon-contact distance measurement instruments can have an operationfrequency of several millions, therefore are widely used in a variety offields. The non-contact distance measurement instruments include activenon-contact distance measurement instruments and passive non-contactdistance measurement instruments. A typical active non-contact distancemeasurement instrument usually projects an energy wave to an object andcomputes a distance between the object and a reference point throughreflection of the energy wave. Common energy waves include visiblelight, high power light beam, ultrasonic wave and X-ray.

SUMMARY OF THE INVENTION

Therefore, the present invention provides a distance measurement methodand a distance measurement system, which can carry out a 3D non-contactdistance measurement and have higher reliability.

In addition, the present invention further provides storage media with aprocessing software, which can process data of the distance measurementsystem, and reliably compute a position of an object.

A distance measurement system provided by the present inventioncomprises a plurality of reference planes, a light source module, animage capture device and a processer module. The light source module iscapable of projecting a light beam with a speckle pattern to thereference planes and an object, so that a plurality of images with thespeckle pattern are shown on the reference planes and a surface of theobject respectively, wherein the speckle pattern has a plurality ofspeckles. Meanwhile, the image capture device captures images having thespeckle pattern shown on the reference planes, so as to generate aplurality of reference image information. In addition, the image capturedevice further captures an image having the speckle pattern shown on thesurface of the object, so as to generate an object image information.The object image information is compared with each of reference imageinformation by the processing module, so as to obtain a plurality ofsimilarity scores. At this time, the processing module would determinewhether or not the highest similarity score is greater than or equal toa threshold value. When the highest similarity score is less than athreshold value, the processing module ignores the distance measurementresult. In contrast, when the highest similarity score is greater thanor equal to the threshold value, the processing module computes theposition of the object according to the position of correspondingreference plane having the highest similarity score.

In one embodiment of the present invention, distances between each ofthe reference planes and next reference plane are the same.

From another viewpoint, a distance measurement method provided by thepresent invention comprises a step of projecting a light beam with aspeckle pattern to a plurality of reference planes and an object, sothat a plurality of images with the speckle pattern are shown on thereference planes and a surface of the object illuminated by the lightbeam, wherein the speckle pattern has a plurality of speckles. Then, theimages with the speckle pattern shown on the reference planes and on thesurface of the object are captured respectively, so as to respectivelygenerate a plurality of reference image information and an object imageinformation. Therefore, the object image information is compared witheach of reference image information, so as to obtain a plurality ofsimilarity scores. Meanwhile, when the highest similarity score is lessthan a threshold value, the distance measurement result is ignored. Inaddition, when the highest similarity score is greater than or equal tothe threshold value, the position of object is computed according to theposition of corresponding reference plane having the highest similarityscore.

From another viewpoint, a storage media with a processing software isprovided. The processing software is configured for performing stepsincluding receiving a plurality of reference image information derivedfrom a plurality of images with a speckle pattern shown on a pluralityof reference planes by reflecting the light beam illuminated onto,wherein the speckle pattern has a plurality of speckles. In addition,the processing software further receives an object image informationderived from an image having the speckle pattern shown on a surface ofan object by reflecting the light beam illuminated onto. Then, theobject image information is compared with each of the reference imageinformation, so as to obtain a plurality of similarity scores. When thehighest similarity score is less than the threshold value, the distancemeasurement result is ignored. In contrast, when the highest similarityscore is greater than or equal to the threshold value, the position ofthe object is computed according to the position of correspondingreference plane having the highest similarity score.

Since the present invention performs the distance measurement based onimages with a speckle pattern reflected by a plurality of referenceplanes and an object, thus a 3D non-contact distance measurement can becarried out. In addition, since the present invention compares the mostsimilarity score with a threshold value, thus a high reliability isobtained.

Other objectives, features and advantages of the present invention willbe further understood from the further technological features disclosedby the embodiments of the present invention wherein there are shown anddescribed preferred embodiments of this invention, simply by way ofillustration of modes best suited to carry out the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore readily apparent to those ordinarily skilled in the art afterreviewing the following detailed description and accompanying drawings,in which:

FIG. 1 is a schematic view of a distance measurement system inaccordance with a first embodiment of the present invention.

FIGS. 2A-2D show images of a speckle pattern reflected by referenceplanes which are spaced a reference point 70, 75, 80, and 85centimeters, respectively.

FIG. 3 shows an image of a speckle pattern reflected by a surface of anobject in accordance with a preferred embodiment of the presentinvention.

FIG. 4 is a schematic view of a distance measurement system inaccordance with a second embodiment of the present invention.

FIG. 5 is a schematic view of a distance measurement system inaccordance with a third embodiment of the present invention.

FIGS. 6A and 6B are flow charts of a distance measurement method inaccordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be described more specifically withreference to the following embodiments. It is to be noted that thefollowing descriptions of preferred embodiments of this invention arepresented herein for purpose of illustration and description only. It isnot intended to be exhaustive or to be limited to the precise formdisclosed.

It is to be understood that other embodiment may be utilized andstructural changes may be made without departing from the scope of thepresent invention. Also, it is to be understood that the phraseology andterminology used herein are for the purpose of description and shouldnot be regarded as limiting. The use of “including,” “comprising,” or“having” and variations thereof herein is meant to encompass the itemslisted thereafter and equivalents thereof as well as additional items.Unless limited otherwise, the terms “connected,” “coupled,” and“mounted,” and variations thereof herein are used broadly and encompassdirect and indirect connections, couplings, and mountings.

FIG. 1 shows a distance measurement system in accordance with a firstembodiment. Referring to FIG. 1, the distance measurement system 100 ofthe present embodiment includes a light source module 102, an imagecapture device 104 and a processing module 106. The light source module102 is capable of providing a light beam having a speckle pattern to adetectable region, wherein the light source module 102 may be a planarlight source module. In addition, the image capture device 104 can becoupled to the processing module 106.

In the present embodiment, the light source module 102 includes a laserlight source 112 and a light diffusing element 114. Wherein, the laserlight source 112 can be a gas laser, e.g., a He—Ne laser, or asemiconductor laser. In addition, the light diffusing element 114 can bea diffusion sheet, a piece of ground glass or a diffraction element.When the laser light source 112 projects a laser light beam 116 to thelight diffusing element 114, the laser beam 116 would be causeddiffraction and interference, so as to form the light beam having thespeckle pattern.

Referring to FIG. 1, in the present embodiment, the light source module102 is capable of projecting the speckle pattern to a plurality ofreference planes, such as the reference planes 122, 124 and 126. In someembodiments, the reference planes 122, 124 and 126 can be parallel witheach other in a viewable region. In other embodiments, distances betweeneach of reference plane spaces and reference plane are the same. Inaddition, in the present embodiment, the reference planes 122, 124 and126 are substantially perpendicular to an optical axis AX-AX′ of thelaser light beam 116, i.e., the optical axis AX-AX′ of the light sourcemodule 102 (such as the planar light source module mentioned above). Inaddition, the reference planes 122, 124, and 126 may be on the opticalaxis AX-AX′ at the same time, or at least one of the reference planes122, 124, and 126 may be not on the optical axis AX-AX′ at the sametime.

When the speckle pattern is projected to the reference planes, each ofthe reference planes 122, 124 and 126 would reflect the light beamhaving the pattern provided from the planar light source module and thenform images of the speckle pattern, which are shown as FIGS. 2A-2D.FIGS. 2A-2D show the images of the speckle pattern reflected by thereference planes spaced a reference point 70, 75, 80, and 85centimeters, respectively. Viewed from FIGS. 2A-2D, the images with thespeckle pattern have a plurality of speckles. At this time, the imagecapture device 104 would capture the images from the reference planes122, 124 and 126, and generate a plurality of reference imageinformation IMGr[1:n] to the processing module 106, wherein n is aninteger greater than 1. In the present embodiment, the image capturedevice 104 may be a video camera or a charge-coupled device. Inaddition, the processing module 106 may be a computer system or aprocessing software installed in a storage media, and is configured foranalyzing the position of the object. Detail principle is specified asfollows.

In some embodiments, the image capture device 104 is placed on areference point O, and is placed at a side of the optical axis AX-AX′.Viewed from FIGS. 2A-2D, each speckle is shown on different positions oneach reference plane. In order to determine the positions of eachspeckle on each reference plane, in the present invention, brightness ofeach speckle is referred. That is, the closer the speckle to the opticalaxis AX-AX′, the brighter the speckle is. In contrast, when the specklesleaves away the optical axis AX-AX′ on different reference planes, thebrightness thereof is decreased. By detecting the brightness of eachspeckle on each reference plane, the position of each speckle on eachreference plane can be obtained.

As environment light impacts on the brightness of the speckle, it mayresult that the processing module 106 gives a wrong determination.Therefore, in some embodiments, the processing module 106 can normalizebrightness values of all of the speckles to eliminate the influence ofthe environment light. In other embodiments, the processing module 106can analysis brightness relations among each speckle and the otherspeckles to constitute brightness information of each speckle. Then thebrightness information can replace the brightness values to be computedby the processing module 106, with which the influence of theenvironment light can be got rid of.

Referring again to FIG. 1, when an object 132 enters into the detectableregion illuminated by the light beam provided from the light sourcemodule 102 (such as the planar light source module mentioned above), asurface of the object 132 which faces the planar light source modulewould reflect the light beam, thus the image having the speckle patternis shown as FIG. 3. FIG. 3 shows the image having the speckle patternreflected by a surface of an object in accordance with a preferredembodiment. In FIG. 3, the images of regions 302 and 304 are the imageswith the speckle pattern reflected by a surface of an object 132. Atthis time, the image capture device 104 would obtain the images from theobject 132, and generate an object image information IMG_(OB) to theprocessing module 106.

When the processing module 106 receives the object image informationIMG_(OB), the object image information IMG_(OB) is compared with each ofreference image information IMGr[1:n] for obtaining a plurality ofsimilarity scores. In some embodiments, the processing module 106 findsthe highest similarity score, and computes the position of the object132 according to the position of the corresponding reference planehaving the highest similarity score. For example, when the distancebetween the position of corresponding reference plane having the highestsimilarity score distances and the reference point O is 80 centimeters,the processing module 106 can compute the position of the object 132distances with the reference point O about 80 centimeters.

In other embodiments, the processing module 106 will choose M thehighest similarity scores for calculation, wherein M is an integergreater than or equal to 2. For example, the processing module 106 willchoose 3 the highest similarity scores, and can more precisely computethe position of the object 132 by an interpolation method.

However, in some situations, environment light, noise, transmissionmistake and so on may impact on the object image information IMG_(OB)generated by the image capture device 104, thus impact on thecalculation of the processing module 106. If the processing module 106computes the position of the object 132 based on error similarityscores, then the calculation may be a mistake. Therefore, in the presentembodiment, when the processing module 106 obtains the said similarityscores from the comparison of the object image information IMG_(OB) withthe reference image information IMGr[1:n], the highest similarity scoreis chosen to compare with a threshold value.

When the processing module 106 determines that the highest similarityscore is less than the threshold value, it may be determined that thehighest similarity score is error, and then the distance measurementthis time is ignored. In contrast, when the processing module 106determines that the highest similarity score is greater than or equal tothe threshold value, then the position of the object 132 can be computedaccording to the position of corresponding reference plane having thehighest similarity score.

FIG. 4 shows a distance measurement system in accordance with a secondembodiment of the present invention. Relative to the first embodiment,in which the image capture device 104 is placed at a side of the opticalaxis AX-AX′, and is located at a position between the laser light source112 and the first reference plane 122, referring to FIG. 4, in thedistance measurement system 400 of the present embodiment, the imagecapture device 104 aims at the optical axis AX-AX′. In addition, in thepresent embodiment, a lens 402 is configured between the laser lightsource 112 and the light diffusing element 114. When the laser lightbeam 116 passes through the lens 402 (such as an extender lens), thelaser light beam 116 will be extended and then reaches the lightdiffusing element 114. Furthermore, a beam splitter 404 is configuredbetween the light diffusing element 114 and the first reference plane122. Therefore, the light reflected from the reference planes 122, 124,126 and the object 132 will be received by the image capture device 104by the help of the beam splitter 404. With this configuration, the imagecapture device 104 aims at the optical axis AX-AX′.

FIG. 5 shows a distance measurement system in accordance with a thirdembodiment of the present invention. Referring to FIG. 5, in thedistance measurement system 500 of the present embodiment, the imagecapture device 104 is arranged beside the laser light source 112.

FIGS. 6A and 6B are flow charts of a distance measurement method inaccordance with a preferred embodiment of the present invention.Referring to FIGS. 6A and 6B, the distance measurement method of thepresent embodiment may first include step S602, i.e., project a lightbeam having a speckle pattern provided from a planar light source moduleto a plurality of reference planes, wherein the speckle pattern has aplurality of speckles. Next, as step S604, capture an image having thespeckle pattern shown on each of the reference planes, so as to obtain aplurality of reference image information associated with the referenceplanes. In addition, go to step S606, project the light beam having thespeckle pattern to an object. Next, go to step S608, capture an imagehaving the speckle pattern shown on a surface of the object illuminatedby the light beam, so as to obtain an object image informationassociated with the object.

Next, go to step S610, compare the object image information with each ofthe reference image information for obtaining a plurality of similarityscores. At this time, go to step S612, determining whether or not thehighest similarity score is greater than or equal to a threshold value.When the highest similarity score is less than a threshold value (i.e.,it is “Not” in the decision of step S612), go to step S614, ignore thedistance measurement. In contrast, when the highest similarity score isgreater than or equal to the threshold value (i.e., it is “Yes” in thedecision of step S612), compute the position of the object according theposition of corresponding reference plane having the highest similarityscore.

Concluded from the above description, the present invention projects asurface light source with a speckle pattern to a plurality of referenceplanes and a surface of an object, then obtains a plurality of referenceimage information associated with the reference planes and an objectimage information associated with the object. After comparing the objectimage information with the reference image information, the plurality ofsimilarity scores are found, and the most similarity score is used tocompute the position of the object. With this way, a 3D non-contactdistance measurement system and method are provided, and the non-contactdistance measurement system and method can have a high reliability.

While the invention has been described in terms of what is presentlyconsidered to be the most practical and preferred embodiments, it is tobe understood that the invention needs not be limited to the disclosedembodiment. On the contrary, it is intended to cover variousmodifications and similar arrangements included within the spirit andscope of the appended claims which are to be accorded with the broadestinterpretation so as to encompass all such modifications and similarstructures.

What is claimed is:
 1. A distance measurement system, comprising: aplurality of reference planes; a light source module, provided a lightbeam having a speckle pattern to the reference planes and an object, sothat a plurality of images having the speckle pattern are shown on thereference planes and a surface of the object respectively, wherein thespeckle pattern has a plurality of speckles; an image capture device,capturing the images having the speckle pattern on each reference planeto generate a plurality of reference image information, and capturingthe image having the speckle pattern on the surface of the object togenerate an object image information; and a processing module, coupledto the image capture device so as to compare the object imageinformation with the reference image information and obtain a pluralityof similarity scores, wherein when the highest similarity score is lessthan a threshold value, the processing module ignores the distancemeasurement result, and when the highest similarity score is greaterthan or equal to the threshold value, the processing module computes theposition of the object according to the position of correspondingreference plane with the highest similarity score.
 2. The distancemeasurement system of claim 1, wherein the light source module comprisesa planar light source module.
 3. The distance measurement system ofclaim 1, wherein the light source module comprises: a laser light,providing a laser light beam; and a light diffusing element, placed in atransmission path of the light beam to perform the light beam having thespeckle pattern.
 4. The distance measurement system of claim 3, whereinthe light diffusing element comprising a diffusion sheet, a piece ofground glass or a diffraction element.
 5. The distance measurementsystem of claim 1, wherein the image capture device comprising a videocamera or a charge-coupled device.
 6. The distance measurement system ofclaim 1, wherein the reference planes are parallel with each other in aviewable region, and are substantially perpendicular to an optical axisof the light source module.
 7. The distance measurement system of claim1, wherein the distances between each of reference planes and nextreference planes are the same.
 8. A distance measurement method,comprising: projecting a light beam having a speckle pattern to aplurality of reference planes and an object, so that a plurality ofimages having the speckle pattern are shown on the reference planes anda surface of the object, wherein the speckle pattern has a plurality ofspeckles; capturing the images having the speckle pattern on each of thereference planes so as to generate a plurality of reference imageinformation; capturing the image having the speckle pattern on thesurface of the object to generate an object image information; comparingthe object image information with each reference image information so asto obtain a plurality of similarity scores; determining whether or notthe highest similarity score is greater than or equal to a thresholdvalue; ignoring the distance measurement result, when the highestsimilarity score is less than the threshold value; and computing theposition of the object according to the position of correspondingreference plane with the highest similarity score, when the highestsimilarity score is greater than or equal to the threshold value.
 9. Thedistance measurement method of claim 8, further comprising: normalizingthe bright of the speckles; computing the position of each of thespeckles on each of the reference image information based on the brightof speckles on each of the reference planes; and comparing the positionof each of the speckles on the object image information with theposition of each of the speckles on each of the reference imageinformation to obtain the similarity scores.
 10. The distancemeasurement method of claim 8, further comprising: comparing brightnessrelationship between each of the speckles and the other specklesrounding the each of the speckles to constitute a brightness informationof each of speckles; computing the position of each of the speckles oneach of the reference image information based on the brightnessinformation; and comparing the position of each of the speckles on theobject image information with the position of each of the speckles oneach of the reference image information to obtain the similarity scores.11. A storage media, having a processing software suitable for adistance measurement system for analyzing a position of an object,wherein the processing software at least performs the following steps:receiving a plurality of reference image information derived from aplurality of images shown on a plurality of reference planes byreflecting a light beam having a speckle pattern, wherein the specklepattern having a plurality of speckles; receiving an object imageinformation derived from an image shown on a surface of an object byreflecting light beam having the speckle pattern; comparing the objectimage information with the reference image information to obtain aplurality of similarity scores; determining whether or not the highestsimilarity score is greater than or equal to a threshold value; ignoringthe distance measurement result, when the highest similarity score isless than the threshold value; and computing the position of the objectaccording to the position of corresponding reference plane having thehighest similarity score, when the highest similarity score is greaterthan or equal to the threshold value.
 12. The storage media of claim 10,wherein the processing software further performs the following steps:normalizing brightness of the speckles to eliminate influence ofenvironment light; computing the position of each of the speckles ineach of the reference image information based on the brightness of eachof speckles on each of the reference planes; and comparing the positionof each of the speckles on the object image information with theposition of each of the speckles on each of the reference imageinformation to obtain the similarity scores.
 13. The storage media ofclaim 10, wherein the processing software is further configured forperforming steps: computing brightness relationship among each of thespeckles and the other speckles to constitute a brightness informationof each of speckles; computing the position of each of the speckles oneach of the reference image information based on the brightnessinformation; and comparing the position of each of the speckles on theobject image information with the position of each of the speckles oneach of the reference image information to obtain the similarity scores.